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Old 03-06-2021, 02:19 PM   #1
Mini-Skoolie
 
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Blowing a fuse

I’m having an issue with my new led lights. I have 10- 6w/0.5A puck lights on 12g wire with a 3-way switch. I was assuming I calculated the fuse needed as 10 x 0.5= 5 amps. I put them on a 5A fuse and I have blown a couple of fuses. I traced the wires and cannot find a short or lose connection. They were just recently put into my fuse block on this fuse size. All my other electrical is fine. When we first installed them we had them connected to our bus’ old dome light wiring and they never stopped working. The bus fuse is 15A. None of the wires feel hot. Can I just increase my fuse size or am I asking for trouble?
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Old 03-06-2021, 03:03 PM   #2
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Yes. At 12 gauge wire you can fuse up to 20 amps.
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Old 03-06-2021, 04:38 PM   #3
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A good idea maybe:
  • Turn the lights on (using a bigger fuse if necessary).
  • Measure voltage at the beginning at the cable run for the lights you are trying to power
  • Measure voltage at the furthest point you can for the same cable.
And report back on those findings.
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Old 03-06-2021, 04:39 PM   #4
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Quote:
Originally Posted by drtbreau View Post
I’m having an issue with my new led lights. I have 10- 6w/0.5A puck lights on 12g wire with a 3-way switch. I was assuming I calculated the fuse needed as 10 x 0.5= 5 amps. I put them on a 5A fuse and I have blown a couple of fuses. *snip* The bus fuse is 15A. None of the wires feel hot. Can I just increase my fuse size or am I asking for trouble?
I'm no expert on electrical, and I know LEDs draw much less current, but 10 x 6W = 60W. And 0.5A x 10 = 5A. So 60W @ 5A, I have to wonder if there's some kind of conflict in anticipated load vs actual load here.
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Old 03-06-2021, 04:49 PM   #5
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A DC clamp on ammeter would be a most useful tool in this situation.
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Old 03-06-2021, 05:47 PM   #6
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You are right in your math 6 watts at 12 volt is 0.5 amps times 10 devices equaling exactly 5 amps. That figure does not allow for the resistance of the wires, the spike when all off those leds come on line or ambient temperature. 12 gauge is good for 20 amps, my suggestion is try a 10 amp fuse.
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Old 03-06-2021, 06:40 PM   #7
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Originally Posted by Rivetboy View Post
You are right in your math 6 watts at 12 volt is 0.5 amps times 10 devices equaling exactly 5 amps. That figure does not allow for the resistance of the wires, the spike when all off those leds come on line or ambient temperature. 12 gauge is good for 20 amps, my suggestion is try a 10 amp fuse.
Yea yep yessir
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